Various reductant fluid delivery systems are known and used in engine applications. In known reductant fluid delivery systems, a reservoir is installed onto a vehicle for containing a supply of the reductant fluid. A pump typically draws the reductant fluid from the reservoir for delivering the drawn reductant fluid to an exhaust after-treatment system downstream of the engine. During operation of the reductant delivery system, unused reductant may be routed back to the reservoir via one or more return lines. It may be advantageous to include a return valve in such a return line so that the return valve can be operated to selectively allow fluid to return to the reservoir when desired.
In some cases, the reductant may be a fluid, for example, an aqueous solution of urea that may have a tendency to crystallize at orifices of the return valve thereby increasing the return valve's susceptibility to clogging. Clogging of the return valve may consequently hamper a flow of unused reductant back into the reservoir and disrupt an otherwise stable operation of the reductant dosing system. However, in extreme cases, excessive pressure build-up could occur upstream of the clogged return valve and such excessive pressure build-up could cause one or more hardware components associated with the reductant fluid delivery system, for example, fluid lines to fail.
PCT Publication WO 2016/144692 thereinafter referred to as “the '692 publication”) discloses a system for purging an exhaust reductant delivery system. However, a manner of working associated with the system of the '692 publication may not be adequately effective in removing crystallized reductant from the valves of the exhaust reductant delivery system. Due to excessive pressure build-up, upstream of the return valves when clogged, known purging systems may continue to render the exhaust reductant delivery system prone to frequent failure and subsequent downtimes owing to maintenance that may be required to bring the exhaust reductant delivery system into operation.
Hence, there is a need for a control system that improves the reliability of a reductant dosing system for use in operation.